New Custom Built PC Not Starting?

Hi I recently built a custom computer and im trying to figure out the problem.

My setup I had before it broke was:

AMD Athlon II x2 3.1 ghz

2 gb ram 1 stick ddr2 crucial 667mhz

1 500gb hdd

1 Hp dvd drive

and a pci-e asus eah5770 1gb gddr5

and a 700 watt ocz mod xtreme pro psu

What happened was i unplugged the psu wires from everything and plugged everything back in because i had tangled some wires so i untangled them. I plugged it in and nothing happens when i hit the power button no click no beep nothing.

Now I thought it was the motherboard so i replaced that and now have a

BIOSTAR TA870+ AM3 ATX

with 8gb of 1333mhz ddr3 ram and the rest is the same.

I'm assuming its the psu as it gets no power or anything if you have any thoughts and can help please let me knowNew Custom Built PC Not Starting?
Make sure you have all of the plugs properly installed and check to see that the voltage is set to the correct amount.New Custom Built PC Not Starting?
Test if it's the power supply by

. unhook the main 24 pin bundle of wires that supplies power to the Mobo. make sure ur power supply is unplugged. Take a paper clip and find the GREEN WIRE. Put one end of the the paper clip into it and the other to the right or left of it. let go of the paper clip, plug in the power supply and if ur power supply turn on. your power supply ok



I've done this many times to diagnose the problemNew Custom Built PC Not Starting?
You need to try another psu before spending any more cash or doing any further fault finding. Your old board is probably still OK. 500watt will be enough.
-Also make sure you have connected the black and yellow 12v axillary wire from psu to the 4 pin connector on the motherboard near the cpu.

swap the reset button wires with power button on the motherboard header pins to make sure it's not a faulty power switch on the case.
First thing that comes to mind is the psu isn't working. I'd double check one more time to make sure that everything is plugged in correctly and that the psu switch is turned on. Try replacing the psu, that's where I'd start. It shouldn't break just by unplugging some wires, though. Seems like a bad connection somewhere.